End-stage liver disease claims about 30,000 lives in the US. Many patients become too ill to tolerate liver transplantation, and even if transplantation were indicated, there is a severe shortage of viable donor organs and only 28% of the wait-listed patients receive transplants. Development and translational studies with novel alternatives to organ transplantation, such as Bioartificial Liver (BAL) devices, cell transplantation and tissu engineered liver substitutes are severely bottlenecked by the lack of a reliable source of viable human hepatocytes. However, a vast pool of unused human cells lies in the discarded donor livers, such as Donors after Cardiac Death (DCD), which are not transplanted due to warm ischemic injury, which significantly reduces transplant success. Recent studies, including those from our group, demonstrate that ischemic and other marginal livers can be reconditioned through extracorporeal Machine Perfusion (MP). The estimated number of such marginally damaged livers that could be rescued and reconditioned for transplantation is ~ 6,000; many more are likely to be too damaged for transplantation, but still viable as a cell source. This immense source of human cells remains unexplored. Our long-term goal is to develop machine perfusion as a way to treat currently unused donor livers and increase donor liver availability for transplantation, cell-based therapeutics and research. The objective of this STTR validation study is to establish human livers disqualified for transplantation because of excessive ischemia, as a reliable source of high quality primary hepatocytes. The central hypothesis to be tested here is that machine perfusion pre-treatment increases the yield of hepatocyte recovery from ischemic human livers. Enhancing the viable yield of hepatocytes from disqualified human donor livers is an innovative endeavor as it capitalizes on the new machine perfusion method developed by our group and increases hepatocyte yield by 25 fold in the rat model. Identifying a reliable human hepatocyte source would dramatically alter the practice in drug discovery and testing by allowing use of human hepatocytes early and at all levels of pharmaceutical testing, reduce reliance on animal models for toxicology, and therefore lead to reduced cost for drug development. Availability of high quality human hepatocytes for a low cost would also eliminate a major bottleneck in realization of cell-based therapies for liver failure.